Disclosed in embodiments herein are systems and methods for engaging cleaning and/or metering blades with image forming machine moving surfaces and more specifically to systems and method of determining and maintaining minimum blade loads needed for preventing image defects.
In electrophotographic image forming applications such as xerography, a charge retentive moving photoreceptor belt, plate, or drum is electrostatically charged according to the image to be produced. In a digital printing image forming machine, an input device such as a raster output scanner controlled by an electronic subsystem can be adapted to receive signals from a computer and to transpose these signals into suitable signals so as to record an electrostatic latent image corresponding to the document to be reproduced on the photoreceptor. In a digital copier, an input device such as a raster input scanner controlled by an electronic subsystem can be adapted to provide an electrostatic latent image to the photoreceptor. In a light lens copier, the photoreceptor may be exposed to a pattern of light or obtained from the original image to be reproduced. In each case, the resulting pattern of charged and discharged areas on moving photoreceptor surface form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image.
The electrostatic image on the moving photoreceptor may be developed by contacting it with a finely divided electrostatically attractable toner. The toner is held in position on the photoreceptor image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original. Once each toner image is transferred to a substrate, and the image is affixed thereto forming a permanent record of the image to be reproduced. In the case of multicolor copiers and printers, the complexity of the image transfer process is compounded, as four or more colors of toner may be transferred to each substrate sheet. Once the single or multicolored toner is applied to the substrate, it is permanently affixed to the substrate sheet by fusing, so as to create the single or multicolor copy or image print.
Following the photoreceptor to substrate toner transfer process, it is necessary to at least periodically clean the charge retentive surface of the moving photoreceptor surface. In order to obtain the highest quality copy or print image, it is generally desirable to clean the photoreceptor each time toner is transferred to the substrate. In addition to removing excess or residual toner, other particles such as paper fibers, toner additives and other impurities (hereinafter collectively referred to as “residue”) that may remain on the charged moving surface of the photoreceptor.
Further, in solid ink imaging systems having intermediate members, ink is loaded into the system in a solid form, either as pellets or as ink sticks, and transported through a feed chute by a feed mechanism for delivery to a heater assembly. A heater plate in the heater assembly melts the solid ink impinging on the plate into a liquid that is delivered to a print head for jetting onto an intermediate member. In the print head, the liquid ink is typically maintained at a temperature that enables the ink to be ejected by the printing elements in the print head, but that preserves sufficient tackiness for the ink to adhere to the intermediate member. In some cases, however, the tackiness of the liquid ink may cause a portion of the ink to remain on the intermediate member after the image is transferred onto the media sheet. This remnant of the jetted image may later degrade other images formed on the intermediate member.
Solid ink jet imaging systems generally use an electronic form of an image to distribute ink melted from a solid ink stick or pellet in a manner that reproduces the electronic image. In some solid ink jet imaging systems, the electronic image may be used to control the ejection of ink directly onto a media sheet. In other solid ink jet imaging systems, the electronic image is used to eject ink onto an intermediate imaging member. A media sheet is then brought into contact with the intermediate imaging member in a nip formed between the intermediate member and a transfer roller. The heat and pressure in the nip helps transfer the ink image from the intermediate imaging member to the media sheet.
One issue arising from the transfer of an ink image from an intermediate imaging member to a media sheet is the transfer of some ink to other machine components. For example, ink may be transferred from the intermediate imaging member to a transfer roller when a media sheet is not correctly registered with the image being transferred to the media sheet. The pressure and heat in the nip may cause a portion of the ink to adhere to the transfer roller, at least temporarily. The ink on the transfer roller may eventually adhere to the back side of a subsequent media sheet. If duplex printing operations are being performed, the quality of the image on the back side is degraded by the ink that is an artifact from a previous processed image.
To address these problems, various release agent applicators have been designed, often as part of an image drum maintenance system. These release agent applicators provide a coating of a release agent, such as silicone oil, onto the intermediate imaging member to reduce the undesired build-up of ink. The amount of release agent applied by such applicators is carefully controlled to achieve a desired amount. Using of too much release agent causes undesirable streak defects, also known as oil streaks, on the output prints.
Release agent applicators typically use a sump system in which a roller is partially immersed in an oil sump. As the release agent roller of an image drum maintenance system rotates out of the sump, it applies release agent to the intermediate imaging member in a desired amount. Prior to the intermediate imaging member reaching the transfer roller nip, the release agent is metered with a blade to achieve the desired thin layer of oil on the intermediate member which does not degrade the media sheet in the nip or cause oil streaks. The excess oil metered from the intermediate member by the blade is directed back into the sump. A blade positioning mechanism is used to bring the blade into contact with the imaging member creating a blade interference with the imaging member that provides a suitable pressure against the blade, referred to as the blade load, sufficient to meter the desired amount of release agent onto the imaging member.
The imaging member is typically a rotating drum formed of a hard material, such as for example aluminum, or other suitable materials. The surface is often etched to provide a suitable texture for good release agent dispersion. The surface is often anodized to provide sufficient hardness for wear. Rather high blade loads are needed to obtain the thin thickness layer of release agent on the drum surface to achieve the desired results. The rough, hard imaging member surfaces and the high blade loads result in the blade having an operational life which is typically shorter than desired. Further, blades perform best, and last the longest, when they are uniformly loaded to the appropriate blade load by the blade positioning mechanism. Part tolerances for the blade positioning mechanism typically require that a blade be loaded higher than may be desired for optimum functioning in order to guarantee achieving an appropriate blade load over the expected life of the blade. These higher blade loads increases blade wear and shorten blade life. The control of the amount of blade load and its uniformity through tighter tolerances in the blade positioning mechanism part adds complexity and cost. Blade material properties can also change over time due to blade relaxation, wear, environmental conditions, and other causes which change the blade loads being applied by the blade positioning mechanism.
The present application provides a new and improved apparatus for cleaning and/or metering a release agent onto an image forming device moving surface which overcomes these above-described problems.